Systems, solid-state mass storage devices, and methods for host-assisted garbage collection

Abstract

Systems and methods suitable for assisting data storage on a solid-state mass storage device by furthering interaction between a host and the solid-state mass storage device. The method includes providing data in a target block from a solid-state mass storage device to a host computer system, analyzing the data to identify valid and invalid data of the data in the target block with the host computer system, removing the invalid data, reformatting the valid data into a new data structure with the host computer system, writing the new data structure to the mass storage device, and marking the data in the target block as invalid.

Description

BACKGROUND OF THE INVENTION[0001]The present invention generally relates to memory media and technologies for use with computers and other processing apparatuses. The invention particularly relates to a solid-state mass storage device using non-volatile, solid-state memory components for permanent storage of data and methods suitable for promoting more efficient storage of data on such devices.[0002]Non-volatile, solid-state memory technologies are widely used in a variety of applications, nonlimiting examples including universal serial bus (USB) drives, digital cameras, mobile phones, smart phones, tablet personal computers (PCs), memory cards, and solid-state drives (SSDs). Non-volatile, solid-state memory technologies used with computers and other processing apparatuses (referred to herein as host computer systems) are currently largely focused on NAND flash memory technologies, with other emerging non-volatile, solid-state memory technologies including phase change memory (PCM),...

AI Technical Summary

Benefits of technology

[0018]Technical effects of the systems, solid-state mass storage devices, and methods described above preferably include the ability to assist and improve the efficiency of garbage collection operations performed on data stored in a solid-state mass storage device. In particular, it is believed that by utilizing a host computer system to analyze valid data pages of a target block of the mass storage device, organize data structures within the pages of the target block that are found to be valid, and then re-writing the valid data structures to new, wholly valid pages in the mass storage device, garbage collection may be assisted by reducing write amplification, increasing performance, and improving endurance of the mass storage device. According to certain embodiments of the invention, the host computer system is capable of analyzing, removing, organizing, and writing data structures within the valid data pages that are smaller than the total capacity of the page in which they reside, i.e., sub-page data. Consequently, valid data pages having invalid data structures therein may undergo garbage collection even if the mass storage device is not aware of the invalid data structures. As such, the system can free up storage space in the mass storage device that would otherwise remain unusable under a conventional page based garbage collection system.

Problems solved by technology

The charging (programming) of the floating gate is unidirectional, that is, programming can only inject electrons into the floating gate, but not release them.

For example, erasing memory cells involves the application of a positive voltage to the device substrate, which does not allow isolation of individual memory cells or even pages, but must be done on a per block basis.

As the flash memory component continues to operate, invalid pages tend to accumulate in blocks that have not been recently erased.

The accumulation of invalid pages generally reduces the amount of total usable storage space available in the flash memory component, and can also slow down the operation of the flash memory component.

As a result of the garbage collection operation, incoming commands (read and write) from a host computer system may be stalled, mainly due to the fact that erasure operations on a flash memory component take much longer to complete than read or write operations and no other operation may be started on a flash memory component until the erasure operation is completed.

At any time while a garbage collection operation is in progress, individual flash memory components may be inaccessible while erasure operations are in progress and access to whole channels may be blocked while page data transfers are in progress.

Therefore, the garbage collection operation, which involves copying valid pages to new locations and block erasure operations, consumes time and resources from the flash memory components and their memory controller, thereby reducing the overall performance of the SSD and hence reducing the Input / Output workload potential of the SSD.

Over an application's lifetime, data structures are continually being inserted and deleted, causing fragmentation across the storage media.

Furthermore, the small sizes of the data structures prevents the application from informing the SSD regarding invalid data since the sizes are generally smaller than the Trim command granularity, that is, an individual page.

However, while not intending to promote a particular interpretation, it appears that the host simply manages and schedules garbage collection within the storage device, but does not take an active role in identifying invalid data.

Further, the issue of data structures that are smaller than the size of a page was not addressed by Kuzmin, that is, the host is not disclosed as analyzing data in a page and identifying sub-page data that is invalid.

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